About Barrier Island Ecosystems

Hello, Adventurers! Welcome to the Coastal Expeditions blog! If you love outdoor activities such as hiking, paddling, exploring nature, and learning about wildlife, you’ve come to the right place! Here on the Coastal Expeditions blog, we dive deep into different habitats, excursions, conservation efforts, and nature programs. To our return readers, thank you for your support! We commend you for being committed to learning. Our site is filled with interactive maps, destination guides, and educational resources. Speaking of educational resources, The Outdoor School consists of afterschool programs, weekly camps, school field trips, and more! We offer hands-on workshops taught by highly-trained guides on wilderness skills, birding, identifying native plants, sustainability, kayaking, and camping. Basically anything you want to learn about, we teach! If you haven’t already, we encourage you to take a look around our site to learn more about our offerings. If you are an educator interested in planning a fun trip for the students at your school, do not hesitate to reach out to us!

In our last article, we tackled the topic of coastal conservation, or “the practice of protecting the natural environment by individuals, organizations, and governments… to conserve natural resources and the existing natural environment and, where possible, to repair damage and reverse trends.” Conservation is responsible for the survival of dozens of species and the existence of several pristine parks and forests across the nation. We focused on conservation efforts along the South Carolina coast to showcase how conservation can make a difference right here at home. Save Crab Bank was a successful conservation effort to rebuild a barrier island in Charleston Harbor–between Shem Creek and Fort Sumter–which had served as a breeding ground for hundreds of shorebirds each year. The Coastal Conservation League, along with the South Carolina Department of Natural Resources, the Coastal Expeditions Foundation, the Army Corp of Engineers, and motivated individuals (like you!) made the restoration of Crab Bank possible. Though the Save Crab Bank project is complete, there are still plenty of ways you can assist with coastal conservation efforts. If you’re interested in learning more, definitely give our last article a read!

Today, we’ll be learning about barrier island ecosystems! As previously mentioned, Crab Bank is one of Charleston’s very own barrier islands. These islands play a vital role in the health of our beaches and the livelihood of hundreds of species. We want to give you an overview of the essential functions of barrier islands, the species they support, and how we can better protect them. We’ll also recommend a few of our tours and field trips which give Adventurers an opportunity to explore South Carolina’s barrier islands and see their incredible splendor for themselves! We hope you enjoy!

A Barrier Island’s Functions

To understand the functions of a barrier island, we must first understand what a barrier island is. What makes a barrier island different from a regular island? Well, barrier islands are positioned parallel to the coast. In this way, barrier islands are able to act as blockades, protecting the mainland from the full intensity of hurricane waves. This is why these islands are known as “barriers.” Barrier islands–of which there are thousands–don’t always stick around long. Since they are constantly being eroded by the brunt of the open ocean, these islands can shift, migrate, or even disappear altogether. Scientists view barrier islands as “geologically transient,” liable to pop up and dissipate just as fast.

Even though most barrier islands were formed over 10,000 years ago, during the Holocene epoch (also known as the Age of Man, which continues to this day), they are still considered young geological features. It’s assumed the significantly slower rise of sea levels during this time is responsible for giving barrier islands an opportunity to develop. Beyond this, barrier islands require an abundance of sand, a gently sloping coastline, and a water system (i.e. waves, currents, tides) strong enough to push the sand. These forces continue to shape barrier islands long after their formation. Scientists believe the barrier islands off of the South Carolina coast have moved anywhere from 40 to 50 miles inland during the Holocene epoch.

South Carolina has thirty-five barrier islands, exceeding every other state (except Florida). Among these barrier islands are commonly known beaches like Isle of Palms, Sullivan’s, Folly, Kiawah, Seabrook, and Hilton Head. Hilton Head, indeed, is half barrier island and half erosion remnant island. Erosion remnant islands are just as they sound–the remnants of eroded mainland. The formation of these types of islands is better understood, with scientists theorizing the melting of Ice Age glaciers led to the flooding of river valleys.

Aside from its protective capabilities, the most notable function of a barrier island is its ability to facilitate the existence of bays, marshes, maritime forests, and wetlands. In other words, when barrier islands hold back the battering waves of the sea, low-energy water systems are able to thrive. These water systems act as habitats to flora and fauna which otherwise wouldn’t be able to thrive there. Now it’s time to learn about these flora and fauna!

The Ecosystem of Barrier Islands

Long and skinny, barrier islands have two: the front-facing side and the back-facing side. The front-facing side is exposed to the ocean’s harsh winds and powerful waves. The back-facing side is protected from the ocean. Due to this, the back-facing side is often the more lively side, teeming with plant life and a flourishing ecosystem. This plant life is fed by an abundance of organic matter in the sediments around the island. The front-facing side has an ecosystem, too, however. Bacteria live between the sand grains and are fed upon by burrowing worms. These worms are fed upon by shorebirds, who also eat crabs and fish. This side of the island is also frequented by filter-feeders, such as mole crabs and clams, who can stand the near-constant saltwater exposure.

The dunes of a barrier island are home to plants, like sea oats and bitter panicum, the roots of which help to maintain the structure of the island. Larger barrier islands–with their own maritime forests–can host sand live oaks and slash pines and magnolias. These forests are home to snakes, foxes, raccoons, deer, squirrels, and–of course–birds. Perhaps more than any other animal, birds enjoy the relative safety and abundant menu of barrier islands. The back-facking side of barrier islands gives way into salt marshes or other brackish environments. The bacteria living in the mud break down dead plant and animal matter into material which can feed the ecosystem, from the bottom up. Small invertebrates and fish are fed on by larger invertebrates and fish, which are then fed on my birds and crabs. Where there’s plenty of food, larger animals–like dolphins, sharks, alligators, and turtles–will also venture.

How We Can Protect Barrier Islands

Barrier islands protect us and therefore we have a responsibility to do what we can to protect them, as well. In addition to natural erosion from storm surge and hurricanes, barrier islands are susceptible to sink due to rising sea levels. On a global scale, slowing the effects of climate change will go a long way towards protecting our barrier islands. On a much smaller scale, restoration projects such as Save Crab Bank are highly effective at prolonging the life of barrier islands. Contributing to the success of projects like these is one way to help protect barrier islands. Barrier islands are also susceptible to erosion from the strong wakes of boats. The building of seawalls and jetties, while good for mainland protection, disrupt the transference of sand to barrier islands, thus weakening them over time. When cities and local governments are considering zoning regulations and building projects, these ramifications should be taken into account.

Our Tours

We host a day-long trip to St. Phillips Island–a 4-mile long barrier island off the coast of Beaufort. This barrier island is pristine, due to the conservation efforts of Ted Turner, and completely undeveloped. The tour consists of a ferry ride to the island, an on-land tour, free time to roam, and a ferry ride back. To read a first-hand account of this tour, you can read our Adventurer’s Log. To learn more about pricing and what to bring, visit here. We also host a kayaking field trip to Crab Bank for middle and high school students, which you can read about here. Our tours are led by knowledgeable, approachable naturalists and sea captains who are eager to answer your questions! We can’t wait to teach you more about barrier island ecosystems. Until next time, readers–get out there and explore! Adventure awaits!